@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.Main_Activity);
    this.setTitle("Title name");
}

如果你想在Java文件中设置标题，那么写在你的活动onCreate

setTitle("Your Title");

如果你想在Manifest里写

    <activity
        android:name=".MainActivity"
        android:label="Your Title" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

在Kotlin中，这样做:

this.title = resources.getText(R.string.fast_learning)

如果你正在使用onCreateOptionsMenu，你也可以在onCreateOptionsMenu中添加setTitle代码。

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);

    setTitle("Neue Aktivität");
    return true;
}

如果你有多个活动，你可以在AndroidManifest.xml中这样设置

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".NumbersActivity"
        android:label="@string/category_numbers"
        android:theme="@style/category_numbers" />
    <activity
        android:name=".FamilyActivity"
        android:label="@string/category_family"
        android:theme="@style/category_family" />
    <activity
        android:name=".ColorsActivity"
        android:label="@string/category_colors"
        android:theme="@style/category_colors" />
    <activity
        android:name=".PhrasesActivity"
        android:label="@string/category_phrases"
        android:theme="@style/category_phrases" />
    <activity
        android:name=".ExperimentActivity"
        android:label="@string/category_experiment"
        android:theme="@style/category_experiment" />
</application>

setTitle(“应用程序”); 在MainActivity.java中更简单 我会说。